The compound 13-oxabicyclo[10.3.0]pentadecane is a valuable fragrance with a warm ambergris note and exceptionally good staying power. The preparation of this substance is described in the Canadian Pat. No. 1,093,568, incorporated herein by reference. The synthesis described can be shown by the following scheme: ##STR1## According to this synthesis, cyclododecanone (I) is converted with bromoacetic acid ester by means of the Reformatsky reaction to the corresponding hydroxy ester (II), which rearranges itself readily into a lactone (III) with heating in a highly acid medium. This lactone is reduced with sodium borohydride in isopropanol to form the diol (IV), from which the 13-oxabicyclo[10.3.0]pentadecane (V) is obtained in the form of a mixture of two stereoisomers in a molar ratio of approximately 2:1 by intramolecular removal of water in toluene, in the presence of p-toluenesulfonic acid (p-TSA).
The use of the highly toxic, volatile bromoacetic acid ester, which irritates the mucous membranes, requires special safeguards obtainable only with a correspondingly expensive technology. Consequently there has been a need for a synthesis that does not utilize bromoacetic acid ester for the introduction of a carboxymethyl group.